In literature, it may be true that happy families are all alike, but Tolstoy’s principle doesn’t really apply to music.

Composers know no limits when it comes to expressing conditions we aspire to — whether happiness, love, or peace and reconciliation. Far from being bland and samey, every harmony — metaphorical and literal — is, to tweak Tolstoy, harmonious in its own way.

That was one of the many strong impressions left by last night’s performance at St. James Cathedral by Seattle Pro Musica (SPM). The program, titled dona nobis pacem, brings SPM’s highly rewarding season to its close with a characteristically bold and stirring send-off (repeat performance tonight, May 20). Its themes of war and peace — timed just ahead of Memorial Day — feel as urgent as ever.

Artistic Director Karen P. Thomas structured the program around Ralph Vaughan Williams’ choral-symphonic masterpiece of the same name, which filled out the second half. The first half comprised a fascinating variety of pieces also centered around the yearning for peace and solace, as well as the grief caused by war and violence. “It is when these themes are addressed that the unmistakable power of music is often mostly keenly felt,” writes Thomas “–to give voice to emotions which are beyond words … and to lift up the human spirit with visions of a better world and a nobler humanity.”

The concert additionally offered a deeply satisfying “status report” on the state of SPM itself — in glowing, radiant health — while displaying its unique strengths across the vocal spectrum. Thus Thomas launched the program with the subchoir Orpheon (the men’s voices) in a rarely heard choral work by Nikolai Golovanov from just before the Bolshevik Revolution. Setting a part of the Orthodox liturgy of St. John Chrysostom — and one of the last surviving compositions of a sacred music tradition that the Soviets sought to wipe out — Mercy of Peace established a mood of supernal calm with exquisitely tapered dynamics.

Next up was the all-women’s Chroma section in a piece SPM commissioned in 2007 from American composer John Muehleisen: Da Pacem, which subtly weaves in references to motets by J.S. Bach. Chroma followed their impassioned account with the ancient plainchant melody Muehleisen used as a basis.

The next subchoir, Vox (mixed voices), turned to the English composer Herbert Howells, familiar in choral circles mostly for his Anglican sacred music. Take Him, Earth, forCherishing, setting a text by the 4th-century Roman Christian poet Aurelius Prudentius Clemens, is a profoundly poignant composition from 1964 dedicated to the memory of the slain J.F. Kennedy (programmed to mark the centenary of JFK’s birth this month). The sense of unforced flow and long-range breathing Thomas commanded from her singers was a textbook example of effective choral phrasing.

Another delight of SPM’s programs is the seamless “staging” of the program’s order. While Chroma sang the mesmerizing canonical repetitions of another Da Pacem chant setting (by the German Renaissance-to-Baroque composer and theorist Johann Christoph Demantius), the full SPM ensemble discreetly gathered to join in for the remainder of the program’s first half.

The beginning words of the traditional Latin Requiem Mass inspired American composer and scholar Peter Winkler to write his musical response to 9/11 for a cappella choir, making powerful use of anguished silences and unexpected breaks in the voices to highlight the sense of desperation.

Thomas’s rich program included several other musical discoveries, such as Canadian composer Eleanor Daley’s 1998 setting of parts of For the Fallen, a poem by Laurence Binyon associated with England’s grieving for its loss at the beginning of World War One. Zachary Lyman’s trumpet offered a touching counterpart to the simple, heartfelt piece.

All season Thomas and SPM have been participating in a season-long celebration of the legacy of the late Bernard Herbolsheimer (who died in January 2016). And what a compelling piece they chose for this program: …for they shall… unfolds as a remarkable harmonic “battle” between the instruments (trumpets and timpani) and the choir, with the former playing martial and aggressive, almost chaotic, passages in strikingly different keys from the singers’ placid recitation of the Beatitudes — two worlds of violently contrasting sound that eventually align on the same key for a brief moment of hope, which is soon undercut by the menace of the timpani.

The Herbolsheimer also served to foreshadow the culminating Vaughan Williams. Ending the first half was another breath of respite in the famous Nunc dimittis from 1915 by Vaughan Williams’ friend Gustav Holst. Thomas paced the music beautifully, making the luminous climax of the work, written for eight-part choir, a destination not just reached but earned.

For the Vaughan Williams, SPM pulled out all the stops, glorying in the powerful emotions, contrasts, and colorful sound worlds of a full-blown symphonic-choral score. It’s not often we get to hear them perform on this scale — and the results were nothing short of thrilling.

dona nobis pacem is a visionary cantata created during a period of worldwide political fear and dread. Vaughan Williams wrote it in 1936, before “the clever hopes … of a low dishonest decade” had expired, to borrow Auden’s phrase. Prime Minister Neville Chamberlain continued to stoke false hopes of appeasement, and Vaughan Williams’ cantata grew increasingly into a warning — another case of art lighting the way unheeded.

The concept behind the work is also advanced and would point the way to a later masterpiece of 20th-century English choral music: Benjamin Britten’s War Requiem for the reconsecration of Coventry Cathedral (bombed in World War Two).

Agnostic (or atheist) that he was, Vaughan Williams is responsible for some of the most beautiful “sacred” music of the last century, including the 1921 Mass in G minor (reflecting his own experiences on the French battlefields in the Great War). dona nobis pacem isn’t a liturgical work by any means, but it exudes a Requiem’s sense of grappling with loss, of coming to terms with grief.

For his text, the composer combined some Biblical texts with poetry by his beloved Walt Whitman (the inspiration for his much earlier A Sea Symphony as well) and a brief speech excerpt from a British politician warning against Britain’s involvement in the 19th-century Crimean War.

The singers were joined by a full orchestral ensemble for the c. 40-minute composition, which began with soprano Tess Altiveros’ moving solo plea for peace (from the Agnus Dei) — a universal plea that soon segued into the concrete terrors catalogued in Whitman’s Beat! Beat! Drums!

Especially in Vaughan Williams’ brass-and-percussion-heavy musical guise — with a few nods to Verdi’s Requiem — the poem’s depiction of “terrible drums” and “bugles” interrupting the peaceable life became a Civil War Dies Irae. (Never mind that a certain U.S. President recently proved to be clueless even as to the basic facts of a war that so profoundly shaped the nation passed down to us.)

Thomas obviously regards this score as a masterwork and had rehearsed the assembled forces in great detail. She also displayed a magnificent theatrical sensibility in the pacing and unfolding of these complex emotions. (I’d be eager to have a chance to hear her conduct for the stage.) The transitions between movements were notably effective, as was the immersive brass climax after “the strong dead-march enwraps me” (in the fourth movement, “Dirge for Two Veterans”).

Baritone solo Matthew Hayward sang with gripping emotion in the third movement (“Reconciliation”), which comes closest to the intimate intensity of Britten’s later War Requiem. Given the challenges of the Cathedral acoustics for combined forces of this size, Thomas judged balances well, allowing for maximum impact at the moment when all hell truly does break loose in the apocalyptic “The Angel of Death.”

From there to the solo soprano’s return at the end — again pleading, imploring for the seemingly unreachable peace — is the endless cycle of humanity’s struggle. But however familiar the pattern, this rousing performance engaged the listener in the urgency of the message, and the vision, in this our time.

One more performance, tonight at 8:00 pm, at St. James Cathedral. Information here.